Many of the critical fabricating procedures associated with producing advanced electronic equipment such as microprocessors and other very large scale integrated (VLSI) circuits are conducted in clean room environments. Complex genetically engineered DNA sequences are also often produced in clean room environments. Continuing advances in fabricating VLSI circuits from a wide variety of semiconductor materials and the remarkable breakthroughs in genetic engineering, have resulted in cleanliness standards of approximately one thousand (1,000) particles per cubic meter of air which may have been acceptable only ten years ago, being unacceptable today. For example, many current VLSI circuits require fabrication in a clean room environment with contamination levels in the range of approximately one to ten particles per cubic meter of air or less.
As acceptable standards for particulate contamination in clean room environments have become more stringent, protective clothing and garments worn by personnel working in such environments have become more elaborate and often more expensive. Typically, clean room garments and accessory items are fabricated from materials which allow reuse following appropriate laundering or cleaning procedures. The combined cost associated with initial purchase, cleaning and storing of reusable garments and accessory items, especially for working environments with very low levels of acceptable particulate contamination, has become a significant factor in the total cost of fabricating the final product in a clean room environment. In several industries, personnel hygiene and potentially hazardous contamination of clean room garments and accessory items are of increasing concern.
A typical clean room garment in 1970 would be a white lab coat or jacket fabricated from high quality cotton. In 1996 this same clean room garment may be fabricated from one or more layers of expanded polytetrafluoroethylene (PTFE) and sandwiched between two or more layers of close knit polyester or woven textile type material. Reusable clean room garments are often formed from such materials by cutting and sewing. Various types of tape and other adhesives have been used to cover the resulting seams to further minimize potential particulate contamination of the clean room environment. One type of material used for such applications includes GORE-TEX plastic films available from W. L. Gore & Associates, Inc., 555 Paper Mill Road, P.O. Box 9329, Newark, Del. 19714.
Until recently, most clean room garments and accessory items were reusable and required cleaning after each use. The effectiveness of such garments and accessory items for clean room applications has often been determined by using the Helmke drum test. Some manufacturers refer to the particulate levels generated by the Helmke drum testing of new clean room garments and accessory items in connection with marketing such clean room garments and accessory items. However, Helmke drum testing is seldom, if ever, performed on clean room garments and accessory items after several cycles of reuse and cleaning.
During the past few years, more disposable products have been used in clean room applications. Many of these disposable products are essentially the same products as used in the medical and healthcare industry. TYVEK.RTM. fabrics, which may be formed at least in part from polyethylene fibers and are available from E.I. duPont Nemours and Company, have been increasingly used in fabricating disposable clean room products. Polyolefin based materials have also been increasingly used for clean room applications. DuPont currently offers clean room wiping materials fabricated from Sontara.RTM. CritiClean.RTM. fabrics.